On Unix-like platforms such as Linux/macOS, there's a Perl script. Make sure you also select libctru and the 3ds examples when installing.

Depending on the kind of homebrew you want to develop, you may be interested in installing and using additional libraries and tools which don't ship alongside devkitARM/libctru. A list of them can be found in Homebrew Libraries and Tools.

You will want to make sure devkitARM is selected during the installation process to develop for the 3DS (and also the DS and GBA) - you can also install devkitPPC (for GameCube/Wii development) and devkitPSP (for PlayStation Portable development) if you wish.

Once the installer has finished, launch MSYS from:

Windows 7 and earlier: Start -> All Programs -> devkitPro -> MSYS

Windows 8 and 8.1: Right click on the Start screen and select 'All Apps'. You should find MSYS there.

Alternatively starting with Windows 10 Anniversary Update (Version 1607), the Windows Subsystem for Linux (WSL) may also be used to run the Linux version of devkitARM. Unless you have some particular need for WSL it's recommended that you stick to a more standard environment.

Currently devkitPro provides precompiled versions of devkitARM for the following Unix-like platforms: Linux (x86/x64), macOS (universal binary). Note that Linux x64 binaries are usable under WSL.

First, you need to install curl so the installer can download the devkitARM packages, and you should also install Git - you'll need it to update libctru or share your code on GitHub, among many other things. If you are running Linux, you'll also need wget; it comes preinstalled on most distributions, but not all.

Find your way into a shell (eg. by opening a Terminal window), and follow the instructions for your OS:

Debian/Ubuntu/Linux Mint/Ubuntu on WSL: sudo apt-get install git curl

Fedora/CentOS/RHEL: sudo yum install git curl

openSUSE: sudo zypper install git curl

Arch Linux/ALWSL: sudo pacman -S git curl wget

macOS: Download Git from [1] and install it. Curl is included with the OS.

Next, we need to download, make executable and run the devkitARM updater (don't worry, the updater is also the installer.)

3DS examples are still being created; however, there are a growing number of examples available from the devkitPro/3ds-examples GitHub repository.
There are now too many to list here in detail, so go ahead and browse them.

To download these, if you installed Git (as you will have if you followed the above instructions), simply type git clone https://github.com/devkitPro/3ds-examples.git into your shell in the directory you wish to store the 3ds-examples folder in.

These can be built from the command line.

To start a new homebrew project from the bash shell, simply type the following (replacing ~/projects/my3dsproject with the place you would like your project to be stored, with ~ meaning your HOME directory):

The standard Makefile will use the folder as the name of the 3dsx that will be built. You can keep that behaviour or simply change the TARGET := $(notdir $(CURDIR)) line in the Makefile to explicitly name your project.

To run it on your 3DS, start the Homebrew Launcher, press Y to open the network loader, then on your PC type: $DEVKITARM/bin/3dslink my3dsproject.3dsx, replacing my3dsproject with the name of the 3dsx file you want to run.)

If all goes well, you'll soon see your application running on your 3DS.